The disclosure relates to a metal sensor and to a method for operating a metal sensor.
Metal sensors for discovering metallic or otherwise magnetizable objects in walls, floors or in the ground are known from the prior art and make use of coils to excite magnetic fields and to measure changes in the magnetic flux. Objects are identified by the fact that the measured changes in flux differ depending on whether a magnetizable object is present or not. The measured change in flux is partially a direct result of the exciting magnetic field and partially the result of the magnetic field emanating from the magnetizable object. In general, the magnetic field emanating from the object is in turn a result of the exciting magnetic field.
A metal sensor is known from the unpublished patent application with the applicant's internal file reference R.335154, which metal sensor comprises two coils which are provided to generate two magnetic fields which are oriented in a mutually opposing manner and the overlap of which almost disappears at the location of a magnetic-field sensor of the metal sensor. As a result, when a magnetizable object is not present, the magnetic-field sensor of the metal sensor detects a zero signal, resulting in an advantageous signal-to-noise ratio and high dynamic response. The zero signal is additionally independent of an ambient temperature. However, if a magnetizable object is present, the measurement signal of the magnetic-field sensor deviates from a zero signal and, in general, is not temperature-independent.